This invention relates to novel pesticide compositions and methods for their use in topical veterinary topical applications. More particularly, this invention is directed to water/perspiration resistant pesticide compositions comprising a solution of a water swellable polycarboxylated polymer and a pesticide in a substantially nonaqueous liquid carrier.
There are many species of biting insects, including mosquitoes, ticks, mites, and horse flies, which prey upon vertebrate species. These insect species not only inflict discomfort by their bites, but they also can transmit disease. The sharp pain associated with insect bites can indirectly result in other injury when, for example, the animal reacts with sudden unexpected reflexive movements. Since the timing of an insect's bite is unpredictable, a docile animal may react in a sudden violent manner. This is especially a problem for equestrians. Horses are frequently bitten by horseflies causing them to bolt unexpectedly, throwing their rider. For these reasons it is desirable to protect vertebrate species, and in particular domesticated animals, from being bitten by insects.
One means of protecting animals from biting insects is to treat the animal with an insecticide or insect repellent. Pesticides suitable for such uses are well known to those familiar with the art, and as used herein the term "pesticide" embraces insecticides, herbicides, fungicides, nematocides, miticides, bactericides, pest repellents, and combinations thereof. Typically, pesticide formulations for veterinary use are applied as a spray, lotion, cream or powder to the animal. Although currently available pesticidal formulations are effective to prevent insects from biting animals, their efficacy is diminished due to their water solubility; as the pesticide treated animal surface (typically hair or skin) comes into contact with water, the pesticide is washed from the treated surface. Topically applied pesticide formulations are often prematurely washed from the treated surface by rain, or as an animal becomes active, the animal's own perspiration. Removal of the applied pesticide renders the animal susceptible to insect attack.
It would thus be desirable to provide a topical pesticide composition for veterinary use that is easy to apply and capable of sustained retention on the treated surface in the presence of water. It is also desirable that such composition be readily washable from the surface when pesticidal functionality is no longer necessary.
The present invention provides a pesticide composition suitable for topical application to an animal or other surface exposed to humid or wet conditions. The composition comprises a solution of a water swellable hydrophilic polymer and a pesticide in a substantially nonaqueous liquid medium. Advantageously, the hydrophilic polymer functions to entrap the pesticide within the polymer matrix and also exhibits good affinity to the surface. The surface applied pesticide formulation is resistant to being washed from the surface by the perspiration of the animal and thus provides prolonged protection from insect bites even while the animal is active. Indeed, ambient humidity and moisture from other sources co-act with the applied pesticide/polymer matrix to swell the matrix and facilitate pesticide release from the matrix.
The present pesticide composition is formulated for rapid evaporation at ambient temperatures. When applied to animal coats, it evaporates to provide a surface adherent layer of the pesticide entrapping polymer matrix. As the animal becomes active, the polymer matrix becomes hydrated, both from animal perspiration and/or from ambient moisture, swells and thereby allows the pesticide to diffuse from the matrix. Thus, the polymer matrix formed during drying of the present composition functions to provide sustained insect protection to the animal not only by increasing the adherence of the pesticide formulation to the animal (more specifically to its skin or surface hair), but also by functioning to gradually release effective quantities of pesticide formulation.
In another embodiment of this invention there is provided the method of prolonging the pesticidal efficacy of a topical pesticide formulation comprising the pesticide in a substantially non-aqueous liquid carrier. The method comprises the step of dissolving about 0.25% to about 10% by volume of a water swellable polycarboxylated polymer in said pesticide formulation. The formulation can be applied topically and after allowing time for the liquid carrier to evaporate, provide prolonged topical pesticidal activity to prevent or reduce insect bites.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.